Perovskite La0.7Ca0.3MnO3 (LCMO) thin films were grown epitaxially on SrTiO3 (STO) and NdGaO3 (NGO) substrates by pulsed laser deposition. The microstructure of these films was investigated by means of high-resolution and Bragg-diffraction contrast transmission electron microscopy. Due to the small lattice mismatch in the system of LCMO/NGO, the films showed a higher Structural perfection than the films on STO Substrates. Misfit dislocations were not detected over large areas in the LCMO film grown on NGO. In contrast, two types of misfit dislocations with Burgers vectors a<010> and a<110> were frequently observed at the LCMO/STO interface. MnO precipitates were identified in the LCMO films by combining energy-dispersive X-ray spectroscopy with electron diffraction analysis. The MnO precipitates were usually formed in the film away from the film/substrate interface. Their size and density increased with the film thickness. (C) 2004 Elsevier B.V. All rights reserved.